should have taken pics when pulling the pumps . . but. so these two nipples that are on the body, L shaped one at top of breaker cap and other one hiding around back in picture that's just above the diaphragm. do they remain open or are they connected to something?

 

The 90 deg is the vent that should be open--the other is an electrical cover for the power lead stud--just isolation from touching ground/earth!

 

Jagstuart

Both these vents are open and are supposed to be connected to plastic breather pipes approximately 400mm long, terminating downwards in a low pressure area of the chassis.

The 90 degree connection is venting the contacts chamber to deter ionization, whilst the steel nipple above the diaphragm is venting the diaphragm chamber to prevent pressure build up behind the diaphragm.

The pump is intended to be mounted with the pulse chamber dome at the top.

 

so norman, where is that "low pressure" area on my '66 3.8 S? and are there diagrams showing routing?

 

Jagstuart

A low pressure area is easy to find on a 1966 3.8 S as the car is fitted with two pumps, one adjacent to each wing (fender) fuel tank. The enclosed area formed by the boot (trunk) side panels, which cover the pumps is a low pressure area. The pump vents can therefore terminate in that area next to the pumps. In the case of a normal chassis mounted S.U fuel pump the ideal would be to vent into one of the chassis box sections not pressurised by the air stream.

One problem you may face on a mid 60's S.Type is a fuel pump passing a quantity of fuel from one tank to the other, you might consider fitting a light spring loaded non return valve down stream of each pump. Although minute dirt particles may hinder 100% blocking of fuel cross feeding, in the main non return valves will stop the majority of unwanted fuel transferring.

I do not know the reason why you have removed the pumps but beware of "faulting" a pump when in fact it is the opposite side pump that has bad seating valves and is misleading you. Of course this only applies to the mid 60's S.Type with twin pumps/tanks.

 

thanks NGW - pumps where not worth rebuilding (though the breakers engaged the diaphragms). found rebuilt or new (as shown in above pic), SUs for $70 by relentless shopping. i've read post about the cross feeding of fuel to tanks causing overflow and will watch for it.